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Topic: Compressed Air V8 Engine (Read 54393 times)

This engine started out being modeled after the 4-cylinder Cirrus engine, but I have since learned it more closely resembles the Whittle V8 engine. These pictures are at the current progress level and I will go back and repost earlier pictures if there is an interest.

Building an engine takes Patience, Planning, Preparation and Machining.Procrastination is nearly the same, but it precludes machining.Thus, an engine will only be built once the procrastination stops and the machining begins!

Here's a picture of the raw stock. I turned a 1" diameter piece of 12L14 down to 13/16" and drilled center holes in each end.

I had to noodle on it a bit to figure out the best way to do it. I decided in the end to turn it between centers. So the first problem was to drill center holes on each end, at 90 degree intervals 1/4" off center. I needed an identical set of holes on each end, and each corresponding pair of holes have to be exactly opposite each other. Luckily, I have a nice tool makers vice that is ground square and flat on all sides, so I was able to clamp the blank in the vice, then use my height gauge to find the center and scribe lines all the way around and a second set at 90 degrees to the first. I also scribed a center line on the face of Jaw #1 on my four jaw chuck. Using the 4-jaw chuck to offset the the work by .25" I drilled the holes, loosening the work and rotating it 90 degrees between holes, lining up the radial line on the end of the blank with the scribed line on the face of the chuck jaw. I think I got them pretty true.

I'm designing this engine as I go, so work may be slow at times. Just hope I can see it through to the end. Tomorrow I start turning the connecting rod journals, saving the mains journals until last.

This is iteration #2 of my crankcase, top half. The first one would probably have worked, but I missed a lot of the dimensions, by a lot, so couldn't in good conscience continue with it.

With this iteration, I've mounted the crankcase half in my dividing head. I will use the rotating motion and lower the end mill a bit at a time to achieve a semicircular, concave cutout in the metal. I think this will give me a lot more consistent result. The metal cuts really nicely so I don't think the long overhang will be a problem. I plan to go slow. Could really use a CNC mill at this point, but this will have to do.

I may shoot a video of part of the process to show how it works. This is work for tomorrow.

I got the crankcase top, 2nd version pretty well finished today and I'm quite happy with the process and the results. I'll be uploading a video showing how I used my dividing head to position the work for hollowing out the inside.

I'm hoping these will have been the most difficult pieces and having them out of the way should make the rest of the project go pretty smoothly (famous last words!).